A two-phase hollow high-entropy oxide catalyst, a preparation method and application thereof

Abstract

The present application relates to the technical fields of high-entropy oxide and electrocatalyst synthesis, and relates to a dual-phase hollow high-entropy oxide catalyst as well as a preparation method and application thereof.The dual-phase hollow high-entropy oxide catalyst comprises metal elements and non-metal elements, wherein the metal elements include ruthenium, nickel, cobalt, iron, manganese and chromium; the non-metal element is oxygen; and the chemical formula of the dual-phase hollow high-entropy oxide catalyst is NiCoFeMnCrRuO.The dual-phase hollow high-entropy oxide catalyst has a multi-shell hollow structure, provides a larger specific surface area, exposes a large number of reaction active sites, and makes the dual-phase hollow high-entropy oxide catalyst have a lower overpotential, a faster reaction efficiency and good electrochemical stability; meanwhile, the preparation method of the dual-phase hollow high-entropy oxide catalyst is simple in process, low in cost, strong in repeatability, suitable for industrial mass production, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-entropy oxides and electrocatalyst synthesis, in particular, to a dual-phase hollow high-entropy oxide catalyst and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen energy, as an efficient and environmentally friendly energy carrier, has attracted more and more attention, and hydrogen energy economy has been vigorously advocated. In order to realize the decarbonization of the energy system, it is inevitable to study the electrolysis of water to produce hydrogen. The electrolysis of water involves HER (hydrogen evolution reaction) and OER (oxygen evolution reaction), and the slow kinetics of the OER process involves four basic steps and four electron transfers, which seriously limits the overall water splitting efficiency and limits its further practical application. Developing efficient electrocatalysts is the key to accelerating the reaction and reducing the electrolysis overpotential. So far, noble metal-based materials are still the most effective electrocatalysts, such as Pt for HER and IrO2 and RuO2 for OER. Although these noble metal electrocatalysts have the best catalytic performance, due to their scarcity and high price, they are still unable to be used for industrial applications. Considering these key shortcomings, exploring noble metal alternative catalysts with low cost, good electrocatalytic performance and sufficient durability is crucial for significantly improving the performance of water electrolysis.

[0003] High-entropy oxides (HEOs) are a class of emerging materials composed of five or more metal elements, which exhibit excellent structural stability and electrochemical performance due to the synergistic effect of their multi-metal components, lattice distortion effect and entropy stabilization characteristics, and have become an important candidate material in the field of electrocatalysis, especially in OER. Their flexible composition and controllability provide a broad space for further optimizing their performance.

[0004] However, relying solely on a single high-entropy oxide is still insufficient to fully meet the needs of high activity and high stability, and more complex structures need to be introduced as a new research direction, and constructing a dual-phase heterostructure is one of the effective strategies.

[0005] Therefore, it is of great significance to develop a dual-phase high-entropy oxide catalyst with low overpotential and fast reaction efficiency. SUMMARY

[0006] The present application aims to overcome the defects of slow reaction of traditional electrocatalysts and the fact that noble metal electrocatalysts cannot be applied to industrial production due to their scarcity and high price, and thus provides a dual-phase hollow high-entropy oxide catalyst, a preparation method and application thereof, the dual-phase hollow high-entropy oxide catalyst having a multi-shell hollow structure, which provides a larger specific surface area and thus exposes a large number of active sites, so that the dual-phase hollow high-entropy oxide catalyst has a lower overpotential, faster reaction efficiency and good electrochemical stability, and the preparation method of the dual-phase hollow high-entropy oxide catalyst is simple in process, low in cost, strong in repeatability, suitable for industrial mass production and has a wide application prospect.

[0007] To achieve the above-mentioned purpose, in a first aspect, the present application provides a dual-phase hollow high-entropy oxide catalyst, the dual-phase hollow high-entropy oxide catalyst comprising metal elements and non-metal elements, wherein,

[0008] The metal elements include ruthenium, nickel, cobalt, iron, manganese and chromium;

[0009] The non-metal element is oxygen;

[0010] The chemical formula of the dual-phase hollow high-entropy oxide catalyst is NiCoFeMnCrRuO.

[0011] Preferably, the particle size of the dual-phase hollow high-entropy oxide catalyst is 0.8 μm~3.5 μm.

[0012] Preferably, the dual-phase hollow high-entropy oxide catalyst has a fluorite / corundum dual-phase heterostructure.

[0013] Preferably, the dual-phase hollow high-entropy oxide catalyst has a multi-shell hollow spherical structure.

[0014] Preferably, the number of shell layers is 1~3.

[0015] Preferably, the shell layer thickness is 100 nm~500 nm.

[0016] In a second aspect, the present application provides a preparation method of a dual-phase hollow high-entropy oxide catalyst, the preparation method comprising:

[0017] 1) mixing a complexing agent with a metal salt in the presence of a solvent to obtain a mixed solution;

[0018] 2) performing a hydrothermal reaction on the mixed solution of step 1) to obtain a precursor microsphere;

[0019] 3) calcining the precursor microsphere of step 2) to obtain a dual-phase hollow high-entropy oxide catalyst.

[0020] Preferably, in step 1), the solvent is water.

[0021] Preferably, the complexing agent is one or two or more of glucose, citric acid and xylitol.

[0022] Preferably, the metal salt is one of five metal salts of ruthenium, nickel, cobalt, iron, manganese and chromium.

[0023] Preferably, the ruthenium salt is ruthenium trichloride and / or ruthenium nitrate.

[0024] Preferably, the nickel salt is selected from one or two or more of nickel chloride, nickel nitrate, nickel sulfate and nickel acetate.

[0025] Preferably, the cobalt salt is selected from one or two or more of cobalt chloride, cobalt nitrate and cobalt sulfate.

[0026] Preferably, the iron salt is selected from one or two or more of iron chloride, iron nitrate and iron sulfate.

[0027] Preferably, the manganese salt is selected from one or two or more of manganese chloride, manganese nitrate, manganese sulfate and manganese acetate.

[0028] Preferably, the chromium salt is selected from one or two or more of chromium chloride, chromium nitrate and chromium sulfate.

[0029] Preferably, in step 1), the concentration of the complexing agent is 15 g / L to 135 g / L.

[0030] Preferably, in step 1), the molar concentration of the ruthenium salt is 5 mmol / L to 55 mmol / L, wherein the ruthenium salt is calculated based on the element ruthenium.

[0031] Preferably, in step 1), the molar concentration of the nickel salt, the cobalt salt, the iron salt, the manganese salt and the chromium salt is 5 mmol / L to 70 mmol / L, wherein the nickel salt is calculated based on the element nickel, the cobalt salt is calculated based on the element cobalt, the iron salt is calculated based on the element iron, the manganese salt is calculated based on the element manganese and the chromium salt is calculated based on the element chromium.

[0032] Preferably, in step 2), the hydrothermal reaction is performed under the conditions of a temperature of 120 ℃ to 220 ℃ and a time of 1 h to 12 h.

[0033] Preferably, in step 2), the particle size of the precursor microspheres is 1 μm to 4 μm.

[0034] Preferably, in step 3), the calcination is performed under the conditions of a temperature of 300 ℃ to 900 ℃, a time of 1 h to 5 h and a heating rate of 1 ℃ / min to 7 ℃ / min.

[0035] In a third aspect, the present application provides a dual-phase hollow high-entropy oxide catalyst prepared by the preparation method of the second aspect, wherein the dual-phase hollow high-entropy oxide catalyst has an oxygen evolution potential of 180 mV-290 mV and a hydrogen evolution potential of 80 mV-180 mV under electrocatalysis at 10 mA / cm 2 In a third aspect, the present application provides a dual-phase hollow high-entropy oxide catalyst prepared by the preparation method of the second aspect, wherein the dual-phase hollow high-entropy oxide catalyst has an oxygen evolution potential of 180 mV-290 mV and a hydrogen evolution potential of 80 mV-180 mV under electrocatalysis at 10 mA / cm

[0036] In a fourth aspect, the present application provides an application of the dual-phase hollow high-entropy oxide catalyst of the first aspect or the dual-phase hollow high-entropy oxide catalyst of the third aspect in the field of water electrolysis.

[0037] In the above technical solution, the present application uses a hydrothermal reaction combined with a calcination strategy to prepare a dual-phase heterojunction multi-shell hollow high-entropy oxide catalyst. First, in the process of hydrothermal reaction, a complexing agent containing a large number of hydroxyl groups is used to complex with metal ions, thereby forming amorphous carbon spheres coated with multiple metal ions; then, by adjusting the high-temperature calcination temperature and the heating rate, the diffusion rate of different metal ions is regulated, thereby forming a multi-shell hollow structure; the hollow multi-shell structure can effectively increase the specific surface area and the number of active sites of the high-entropy oxide; further, by adjusting the content of the ruthenium precursor, the high-entropy oxide can realize the evolution process from a single-phase corundum structure to a dual-phase corundum type / fluo-type heterostructure and then to a single-phase fluo-type structure; the dual-phase heterostructure can effectively promote the rapid conversion of intermediates and accelerate the reaction kinetics; at the same time, the introduction of the high-entropy strategy can effectively improve the stability of the electrocatalytic reaction, and the dual-phase heterostructure exhibits excellent electrocatalytic oxygen evolution reaction (OER) and electrocatalytic hydrogen evolution reaction (HER) performance.

[0038] At the same time, the preparation method of the dual-phase hollow high-entropy oxide catalyst of the present application has simple process, low cost, strong repeatability, is suitable for industrial mass production, and has broad application prospect.

[0039] Moreover, the dual-phase hollow high-entropy oxide catalyst of the present application has a fluo-type / corundum-type crystal phase and a multi-shell, hollow spherical morphology. With the synergistic effect of multiple metal components, the lattice distortion effect and the entropy stabilization characteristics, the dual-phase hollow high-entropy oxide catalyst exhibits excellent structural stability and electrochemical performance. Through element design, the composition and phase structure of the high-entropy oxide can be regulated to improve its catalytic performance. On this basis, the design of the multi-shell hollow microsphere structure increases the specific surface area and the reaction active sites, thereby improving the electrocatalytic reaction activity.

[0040] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0041] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0042] Figure 1 SEM photograph of the high-entropy oxide precursor prepared in Example 5, wherein, Figure 1 the magnification of (a) is 7000 times, Figure 1 the magnification of (b) is 15000 times;

[0043] Figure 2 SEM photograph of the dual-phase hollow high-entropy oxide catalyst prepared in Example 5; wherein, Figure 2 the magnification of (a) is 6000 times, Figure 2 the magnification of (b) is 35000 times;

[0044] Figure 3 XRD spectrum of the dual-phase hollow high-entropy oxide catalyst prepared in Example 5;

[0045] Figure 4 Results of structure and element analysis of the dual-phase hollow high-entropy oxide catalyst prepared in Example 5; wherein, Figure 4 (a) is a TEM photograph of the dual-phase hollow high-entropy oxide catalyst prepared in Example 5, Figure 4 (b) is a HRTEM photograph of the dual-phase hollow high-entropy oxide catalyst prepared in Example 5, Figure 4 (c) is a HADDF and EDS element distribution photograph of the dual-phase hollow high-entropy oxide catalyst prepared in Example 5;

[0046] Figure 5 Results of hydrogen evolution oxygen reduction performance test of the dual-phase hollow high-entropy oxide catalyst prepared in Examples 5-6 and the catalyst prepared in Comparative Examples 1-2; wherein, Figure 5 (a) is an LSV curve of OER of the dual-phase hollow high-entropy oxide catalyst prepared in Examples 5-6 and the catalyst prepared in Comparative Examples 1-2 in 1 M KOH solution; Figure 5 (b) is an LSV curve of HER of the dual-phase hollow high-entropy oxide catalyst prepared in Examples 5-6 and the catalyst prepared in Comparative Examples 1-2 in 1 M KOH solution. DETAILED DESCRIPTION

[0047] The specific embodiments of the present application are described below in detail. It should be understood that the specific embodiments described herein are merely illustrative and explanatory of the application and are not intended to limit the application.

[0048] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to sub-ranges falling within the specified range. In this context, individual points within a range should not be dismissed from the range merely because the points are also within another range.

[0049] In a first aspect, the present application provides a dual-phase hollow high-entropy oxide catalyst, the dual-phase hollow high-entropy oxide catalyst comprising metal elements and non-metal elements, wherein,

[0050] The metal elements comprise ruthenium, nickel, cobalt, iron, manganese and chromium;

[0051] The non-metal element is oxygen;

[0052] The chemical formula of the dual-phase hollow high-entropy oxide catalyst is NiCoFeMnCrRuO.

[0053] The present application utilizes a hydrothermal reaction combined with a calcination strategy to prepare a dual-phase heterojunction multi-shell hollow high-entropy oxide catalyst. First, in the process of hydrothermal reaction, a complexing agent containing a large number of hydroxyl groups is used to complex with metal ions, thereby forming amorphous carbon spheres coated with multiple metal ions; then by adjusting the high-temperature calcination temperature and the heating rate to control the diffusion rate of different metal ions, a multi-shell hollow structure is formed, the hollow multi-shell structure can effectively increase the specific surface area and the number of active sites of the high-entropy oxide; further by adjusting the content of the ruthenium precursor, the evolution process of the high-entropy oxide from a single-phase corundum structure to a dual-phase corundum type / fluo-type heterostructure and then to a single-phase fluo-type structure is realized, the dual-phase heterostructure can effectively promote the rapid conversion of intermediates and speed up the reaction kinetics; at the same time, the introduction of the high-entropy strategy can effectively improve the stability of the electrocatalytic reaction, and excellent electrocatalytic oxygen evolution reaction (OER) and electrocatalytic hydrogen evolution reaction (HER) performance are exhibited.

[0054] In a preferred embodiment of the present application, the particle size of the dual-phase hollow high-entropy oxide catalyst is 0.8 μm to 3.5 μm.

[0055] In a preferred embodiment of the present application, the dual-phase hollow high-entropy oxide catalyst has a fluo-type / corundum-type dual-phase heterostructure.

[0056] In a preferred embodiment of the present application, the dual-phase hollow high-entropy oxide catalyst has a multi-shell hollow spherical structure.

[0057] In a preferred embodiment of the present application, the number of shell layers is 1 to 3, which can be 1, 2 or 3.

[0058] In a preferred embodiment of the present application, the shell layer has a thickness of 100 nm to 500 nm.

[0059] In a second aspect, the present application provides a preparation method of the dual-phase hollow high-entropy oxide catalyst, which comprises:

[0060] 1) mixing a complexing agent with metal salts in the presence of a solvent to obtain a mixed solution;

[0061] 2) performing a hydrothermal reaction on the mixed solution of step 1) to obtain a precursor microsphere;

[0062] 3) calcining the precursor microsphere of step 2) to obtain the dual-phase hollow high-entropy oxide catalyst.

[0063] The preparation method of the dual-phase hollow high-entropy oxide catalyst of the present application has simple process, low cost, strong repeatability, is suitable for industrial mass production, and has broad application prospect.

[0064] In a preferred embodiment of the present application, in step 1), the solvent is water, which can be deionized water, ultrapure water or distilled water.

[0065] In a preferred embodiment of the present application, in order to ensure uniform dispersion of metal ions in the hydrothermal process and form stable precursors, and at the same time increase the specific surface area and active sites by constructing a multi-shell hollow structure through the carbonization process, in step 1), the complexing agent is one or more of glucose, citric acid and xylitol, preferably glucose. These complexing agents all contain polyhydroxy or carboxyl groups and have metal complexing ability. The hydroxyl groups thereof are complexed with metal ions to form a precursor microsphere, and a multi-shell hollow structure is formed after calcination.

[0066] In a preferred embodiment of the present application, in order to construct a high-entropy oxide system through the synergistic effect of multi-metal components, in step 1), the metal salt is a ruthenium salt, a nickel salt, a cobalt salt, an iron salt, a manganese salt and a chromium salt.

[0067] In a preferred embodiment of the present application, in step 1), the ruthenium salt is ruthenium trichloride and / or ruthenium nitrate, for example, it can be ruthenium trichloride, ruthenium nitrate or a mixture of ruthenium trichloride and ruthenium nitrate.

[0068] In a preferred embodiment of the present application, in step 1), the nickel salt is selected from one or more of nickel chloride, nickel nitrate, nickel sulfate and nickel acetate, for example, it can be nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, a mixture of nickel chloride and nickel nitrate, a mixture of nickel chloride and nickel sulfate, a mixture of nickel chloride and nickel acetate, or a mixture of nickel nitrate and nickel sulfate, etc.

[0069] In a preferred embodiment of the present application, in step 1), the cobalt salt is selected from one or more of cobalt chloride, cobalt nitrate and cobalt sulfate, for example, it can be cobalt chloride, cobalt nitrate, cobalt sulfate, a mixture of cobalt chloride and cobalt nitrate, a mixture of cobalt chloride and cobalt sulfate, or a mixture of cobalt nitrate and cobalt sulfate, etc.

[0070] In a preferred embodiment of the present application, in step 1), the iron salt is selected from one or more of iron chloride, iron nitrate and iron sulfate, for example, it can be iron chloride, iron nitrate, iron sulfate, a mixture of iron chloride and iron nitrate, a mixture of iron chloride and iron sulfate, or a mixture of iron nitrate and iron sulfate, etc.

[0071] In a preferred embodiment of the present application, in step 1), the manganese salt is selected from one or more of manganese chloride, manganese nitrate, manganese sulfate and manganese acetate, for example, it can be manganese chloride, manganese nitrate, manganese sulfate, manganese acetate, a mixture of manganese chloride and manganese nitrate, a mixture of manganese chloride and manganese sulfate, a mixture of manganese chloride and manganese acetate, or a mixture of manganese nitrate and manganese sulfate, etc.

[0072] In a preferred embodiment of the present application, in step 1), the chromium salt is selected from one or more of chromium chloride, chromium nitrate and chromium sulfate, for example, it can be chromium chloride, chromium nitrate, chromium sulfate, a mixture of chromium chloride and chromium nitrate, a mixture of chromium chloride and chromium sulfate, or a mixture of chromium nitrate and chromium sulfate, etc.

[0073] In a preferred embodiment of the present application, in step 1), the concentration of the complexing agent is 15 g / L-135 g / L, for example, it can be 15 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L or 130 g / L.

[0074] In a preferred embodiment of the present application, in step 1), the molar concentration of the ruthenium salt is 5 mmol / L-55 mmol / L, wherein the ruthenium salt is calculated based on the element ruthenium, for example, it can be 5 mmol / L, 10 mmol / L, 15 mmol / L, 20 mmol / L, 25 mmol / L, 30 mmol / L, 40 mmol / L, 50 mmol / L or 55 mmol / L.

[0075] In a preferred embodiment of the present application, in step 1), the molar concentration of the nickel salt, the cobalt salt, the iron salt, the manganese salt and the chromium salt is 5 mmol / L to 70 mmol / L, wherein the nickel salt is calculated based on the element nickel, the cobalt salt is calculated based on the element cobalt, the iron salt is calculated based on the element iron, the manganese salt is calculated based on the element manganese, and the chromium salt is calculated based on the element chromium, for example, it can be 5 mmol / L, 10 mmol / L, 20 mmol / L, 30 mmol / L, 35 mmol / L, 40 mmol / L, 50 mmol / L or 70 mmol / L.

[0076] In a preferred embodiment of the present application, in step 2), the conditions of the hydrothermal reaction include a temperature of 120 ℃ to 220 ℃ and a time of 1 h to 12 h, for example, the temperature can be 120 ℃ and the time can be 1 h, the temperature can be 130 ℃ and the time can be 2 h, the temperature can be 150 ℃ and the time can be 3 h, the temperature can be 160 ℃ and the time can be 5 h, the temperature can be 170 ℃ and the time can be 6 h, the temperature can be 180 ℃ and the time can be 8 h, or the temperature can be 220 ℃ and the time can be 12 h.

[0077] In a preferred embodiment of the present application, in step 2), the particle size of the precursor microspheres is 1 μm to 4 μm.

[0078] In a preferred embodiment of the present application, in step 2), after the hydrothermal reaction, the precursor microspheres are cooled to room temperature, filtered and washed, and then dried.

[0079] In a preferred embodiment of the present application, the drying conditions include drying in an oven at 30 ℃ to 60 ℃ for 1 h to 10 h.

[0080] In a preferred embodiment of the present application, in step 3), the calcination conditions include a temperature of 300 ℃ to 900 ℃, a time of 1 h to 5 h, and a heating rate of 1 ℃ / min to 7 ℃ / min.

[0081] In a third aspect, the present application provides a dual-phase hollow high-entropy oxide catalyst prepared by the preparation method of the second aspect, wherein the dual-phase hollow high-entropy oxide catalyst has an electrocatalytic oxygen evolution potential of 180 mV to 290 mV and an electrocatalytic hydrogen evolution potential of 80 mV to 180 mV in 1 M KOH under a current density of 10 mA / cm 2

[0082] In a fourth aspect, the present application provides a use of the dual-phase hollow high-entropy oxide catalyst of the first aspect or the dual-phase hollow high-entropy oxide catalyst of the third aspect in the field of water electrolysis.

[0083] ​The dual-phase hollow high-entropy oxide catalyst of the application has a crystal phase of fluorite type / sapphire type, has a multi-shell, hollow spherical morphology structure. With the synergistic effect of the multi-metal components, the lattice distortion effect and the entropy stability characteristics, excellent structural stability and electrochemical performance are exhibited. Through element design, the components and phase structure of the high-entropy oxide can be adjusted to improve the catalytic performance. On this basis, the design of the multi-shell hollow microsphere structure is adopted to increase the specific surface area and the reaction active sites, so as to improve the electrocatalytic reaction activity.

[0084] In the application, the room temperature is 15-30 ℃.

[0085] The application will be described in detail below by examples. In the following examples, the drugs and medicaments are all conventional commercially available products.

[0086] Example 1

[0087] 1.0 g of anhydrous glucose was dispersed in 30 mL of deionized water, stirred for 10 min to obtain a glucose solution, and then equal moles (0.4 mmol) of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O and 0.4 mmol of RuCl3 were added to the glucose solution. After being mixed uniformly, the mixture was transferred to a 100 mL polytetrafluoroethylene reaction kettle, heated to 120 ℃, and reacted for 12 h. After being cooled to room temperature, the mixture was filtered and washed, and then dried in a 30 ℃ oven for 10 h to obtain a high-entropy oxide precursor.

[0088] The high-entropy oxide precursor was placed in a muffle furnace and heated to 300 ℃ at a heating rate of 1 ℃ / min, and calcined for 5 h. The obtained product was a dual-phase hollow high-entropy oxide catalyst, which was recorded as F / C-HEO-1.

[0089] Example 2

[0090] 1.5 g of anhydrous glucose was dispersed in 30 mL of deionized water, stirred for 10 min to obtain a glucose solution, and then equal moles (0.8 mmol) of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O and 0.7 mmol of RuCl3 were added to the glucose solution. After being mixed uniformly, the mixture was transferred to a 100 mL polytetrafluoroethylene reaction kettle, heated to 140 ℃, and reacted for 10 h. After being cooled to room temperature, the mixture was filtered and washed, and then dried in a 40 ℃ oven for 8 h to obtain a high-entropy oxide precursor.

[0091] The high-entropy oxide precursor was placed in a muffle furnace, and heated to 400 ℃ at a heating rate of 2 ℃ / min, and calcined for 3 h. The obtained product was a dual-phase hollow high-entropy oxide catalyst, denoted as F / C-HEO-2.

[0092] Example 3

[0093] 1.8 g of anhydrous glucose was dispersed in 40 mL of deionized water, stirred for 10 min to obtain a glucose solution, and equal moles (1.2 mmol) of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O and 1.1 mmol of RuCl3 were added to the glucose solution. After mixing, it was transferred to a 100 mL polytetrafluoroethylene reactor, heated to 160 ℃, and reacted for 6 h. After cooling to room temperature, it was suction filtered and washed, and dried in a 60 ℃ oven for 4 h to obtain a high-entropy oxide precursor.

[0094] The high-entropy oxide precursor was placed in a muffle furnace, and heated to 600 ℃ at a heating rate of 3 ℃ / min, and calcined for 3 h. The obtained product was a dual-phase hollow high-entropy oxide catalyst, denoted as F / C-HEO-3.

[0095] Example 4

[0096] 3 g of anhydrous glucose was dispersed in 50 mL of deionized water, stirred for 10 min to obtain a glucose solution, and equal moles (1.6 mmol) of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O and 1.3 mmol of RuCl3 were added to the glucose solution. After mixing, it was transferred to a 100 mL polytetrafluoroethylene reactor, heated to 180 ℃, and reacted for 4 h. After cooling to room temperature, it was suction filtered and washed, and dried in a 60 ℃ oven for 2 h to obtain a high-entropy oxide precursor.

[0097] The high-entropy oxide precursor was placed in a muffle furnace, and heated to 700 ℃ at a heating rate of 5 ℃ / min, and calcined for 2 h. The obtained product was a dual-phase hollow high-entropy oxide catalyst, denoted as F / C-HEO-4.

[0098] Example 5

[0099] 4 g of anhydrous glucose was dispersed in 60 mL of deionized water and stirred for 10 min to obtain a glucose solution. Equimolar amounts (2 mmol) of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O and 1.4 mmol of RuCl3 were added to the glucose solution. After mixing evenly, the mixture was transferred to a 100 mL polytetrafluoroethylene reactor, heated to 220 °C, and reacted for 1 h. After cooling to room temperature, the mixture was filtered, washed, and dried in an oven at 50 °C for 7 h to obtain a high-entropy oxide precursor.

[0100] The high-entropy oxide precursor was placed in a muffle furnace and heated to 900 °C at a heating rate of 7 °C / min, and calcined for 1 h. The resulting product was a two-phase hollow high-entropy oxide catalyst, denoted as F / C-HEO-5.

[0101] Depend on Figure 1 The SEM image of the high-entropy oxide precursor prepared in Example 5 shows that the high-entropy oxide precursor of the present invention has a spherical structure.

[0102] Depend on Figure 2 As can be seen from the SEM image of the biphase hollow high-entropy oxide catalyst prepared in Example 5 of the present invention, the biphase hollow high-entropy oxide catalyst prepared in Example 5 of the present invention has a uniform morphology and size, forms an obvious hollow structure, and its shell is dense.

[0103] Depend on Figure 3 As can be seen from the XRD pattern of the biphase hollow high-entropy oxide catalyst prepared in Example 5 of the present invention, the biphase hollow high-entropy oxide catalyst prepared in Example 5 of the present invention has a biphase heterostructure with fluorite-type structure and corundum-type structure.

[0104] Depend on Figure 4 (a) TEM image of the biphase hollow high-entropy oxide catalyst prepared in Example 5 and Figure 4 (b) The HRTEM image of the biphase hollow high-entropy oxide catalyst prepared in Example 5 shows that the biphase hollow high-entropy oxide catalyst prepared in Example 5 of the present invention has a uniform morphology and size, is a hollow core-shell structure, and forms a fluorite / corundum biphase structure. Figure 4 (c) The HADDF and EDS elemental distributions of the biphase hollow high-entropy oxide catalyst prepared in Example 5 show that the biphase hollow high-entropy oxide catalyst prepared in Example 5 of this invention contains Fe, Co, Ni, Cr, Mn, Ru, C and O elements.

[0105] Example 6

[0106] The 1.8 g of anhydrous glucose was dispersed in 30 mL of deionized water, stirred for 10 min to obtain a glucose solution, and then 1.65 mmol of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O, and 1.2 mmol of RuCl3 were added to the glucose solution. After being uniformly mixed, the mixture was transferred into a 100 mL polytetrafluoroethylene reactor, heated to 160 ℃, and reacted for 12 h. After being cooled to room temperature, the mixture was filtered and washed, and then dried in a 60 ℃ oven for 3 h to obtain a high-entropy oxide precursor.

[0107] The high-entropy oxide precursor was placed in a muffle furnace and heated to 700 ℃ at a rate of 3 ℃ / min, and calcined for 3 h. The obtained product was a dual-phase hollow high-entropy oxide catalyst, denoted as F / C-HEO-6.

[0108] Comparative Example 1

[0109] The 1.8 g of anhydrous glucose was dispersed in 30 mL of deionized water, stirred for 10 min to obtain a glucose solution, and then 1.65 mmol of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O were added to the glucose solution. After being uniformly mixed, the mixture was transferred into a 100 mL polytetrafluoroethylene reactor, heated to 160 ℃, and reacted for 12 h. After being cooled to room temperature, the mixture was filtered and washed, and then dried in a 60 ℃ oven for 3 h to obtain a high-entropy oxide precursor.

[0110] The high-entropy oxide precursor was placed in a muffle furnace and heated to 700 ℃ at a rate of 3 ℃ / min, and calcined for 3 h. The obtained product was a single-phase corundum-type multi-shell hollow high-entropy oxide catalyst, denoted as C-HEO.

[0111] Comparative Example 2

[0112] The 1.8 g of anhydrous glucose was dispersed in 30 mL of deionized water, stirred for 10 min to obtain a glucose solution, and then 1.65 mmol of NiCl2·6H2O, CoCl2·6H2O, FeCl3·6H2O, MnCl2·4H2O, CrCl3·6H2O, and 1.6 mmol of RuCl3 were added to the glucose solution. After being uniformly mixed, the mixture was transferred into a 100 mL polytetrafluoroethylene reactor, heated to 160 ℃, and reacted for 12 h. After being cooled to room temperature, the mixture was filtered and washed, and then dried in a 60 ℃ oven for 3 h to obtain a high-entropy oxide precursor.

[0113] The high-entropy oxide precursor was placed in a muffle furnace, and heated to 700 ℃ at a heating rate of 3 ℃ / min, and calcined for 3h, and the obtained product was a single-phase fluorite-type multi-shell hollow high-entropy oxide catalyst, denoted as F-HEO.

[0114] Table 1

[0115]

[0116] Application Example 1

[0117] The dual-phase hollow high-entropy oxide catalysts prepared in Examples 1-6 and the catalyst prepared in Comparative Examples 1-2 were respectively ground for 1h, 10 mg of each was mixed with 1 mL of a mixed solution of water and isopropyl alcohol (the volume ratio of water to isopropyl alcohol was 3:1) and 50 μL of a Nafion solution, and ultrasonic dispersion was performed for 30 min to obtain a dispersion liquid;

[0118] Then, 10 μL of the above dispersion liquid was applied to a working electrode, the electrode was dried at room temperature, 1 M KOH solution was used as an electrolyte, a stone mill rod was used as a counter electrode, Ag / AgCl was used as a reference electrode, a three-electrode system was formed with the above working electrode, and water electrolysis performance test was performed.

[0119] Detection Example 1

[0120] The three-electrode system composed of the dual-phase hollow high-entropy oxide catalysts prepared in Examples 1-6 and the catalyst prepared in Comparative Examples 1-2 used in Application Example 1 as water electrolysis catalysts was tested in 1 M KOH solution at a current density of 10 mA·cm -2 , and the oxygen evolution potential (OER) and the hydrogen evolution potential (HER) were measured, and the results are shown in Table 2 and Figure 5 .

[0121] Table 2

[0122]

[0123] In the table, “—” indicates that the catalyst cannot reach a current density of 10 mA / cm 2 in the tested potential range, indicating that its catalytic activity is extremely low and cannot effectively promote the OER and HER reactions.

[0124] From the data in Table 2 and the content of Figure 5 , it can be found that the dual-phase hollow high-entropy oxide catalyst prepared in Example 5 has excellent water electrolysis performance due to the hollow structure and dual-phase structure, and can reach a current density of 10 mA·cm -2The OER overpotential is 275 mV and the HER overpotential is 138 mV at a current density of 10 mA·cm-2. The OER and HER performances of Examples 1-4 and Example 6 are all poorer than that of Example 5, because the amount of ruthenium salt used in the preparation of the dual-phase hollow high-entropy oxide catalysts of Examples 1-4 and Example 6 is lower than that of Example 5, and the hydrothermal and calcination process parameters deviate from the optimal values, resulting in incomplete hollow shell structure, reduced dual-phase interface area, and affecting the performance.

[0125] The catalyst prepared in Comparative Example 1 has insufficient OER / HER active sites due to the absence of ruthenium, slow reaction kinetics, weak conductivity of pure metal oxide, and low electron transport efficiency, which cannot reach a current density of 10 mA·cm -2 The catalyst prepared in Comparative Example 1 has insufficient OER / HER active sites due to the absence of ruthenium, slow reaction kinetics, weak conductivity of pure metal oxide, and low electron transport efficiency, which cannot reach a current density of 10 mA·cm

[0126] The catalyst prepared in Comparative Example 2 has poor catalytic activity due to the incorporation of excess ruthenium, which causes complete conversion to fluorite phase, loss of stability support of corundum phase, and easy structural collapse in the cycle.

[0127] In summary, the dual-phase heterojunction multi-shell hollow high-entropy oxide catalyst is prepared by using a hydrothermal reaction combined with a calcination strategy. First, in the hydrothermal reaction process, a complexing agent containing a large number of hydroxyl groups is used to complex with metal ions, thereby forming amorphous carbon spheres coated with multiple metal ions. Then, by adjusting the high-temperature calcination temperature and the heating rate to control the diffusion rate of different metal ions, a multi-shell hollow structure is formed. The hollow multi-shell structure can effectively increase the specific surface area and the number of active sites of the high-entropy oxide, providing a new path for performance improvement of the dual-phase high-entropy oxide, achieving low overpotential, fast reaction efficiency, and excellent electrochemical stability.

[0128] Further, by controlling the ratio and composition of different metal ions, the phase structure of the dual-phase high-entropy oxide is controlled, thereby widening its application field. By adjusting the content of the ruthenium precursor, the high-entropy oxide evolves from a single-phase corundum structure to a dual-phase corundum / fluorite heterostructure and then to a single-phase fluorite structure. The dual-phase heterostructure can combine the advantages of different components and optimize the electronic structure of the active sites through the interface synergistic effect, thereby improving the adsorption capacity of the reaction intermediates and significantly improving the catalytic performance.

[0129] The above describes the preferred embodiments of the present application in detail, but the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, and these simple modifications all belong to the protection scope of the present application.

[0130] It should be further noted that the various technical features described in the above detailed description can be combined in any suitable manner without departing from the scope of the application. To avoid not necessary repetition regarding various combinations, no further combinations will be described.

[0131] Furthermore, the various embodiments of the application can also be combined with each other, as long as it does not violate the idea of the application, it should also be considered as disclosed by the present application.

Claims

1. A two-phase hollow high-entropy oxide catalyst, characterized in that, The dual-phase hollow high-entropy oxide catalyst comprises metal elements and non-metal elements, wherein, the metal elements include ruthenium, nickel, cobalt, iron, manganese and chromium; the non-metal element is oxygen; the chemical formula of the dual-phase hollow high-entropy oxide catalyst is NiCoFeMnCrRuO; the dual-phase hollow high-entropy oxide catalyst has a fluorite / corundum dual-phase heterostructure; the dual-phase hollow high-entropy oxide catalyst has a multi-shell hollow sphere structure; the number of the shell layers is 2-3.

2. The dual-phase hollow high-entropy oxide catalyst of claim 1, wherein, the particle size of the dual-phase hollow high-entropy oxide catalyst is 0.8-3.5 μm.

3. The dual-phase hollow high-entropy oxide catalyst according to claim 1 or 2, wherein, the thickness of the shell layer is 100-500 nm.

4. A method of preparing a two-phase hollow high-entropy oxide catalyst, characterized by, the preparation method comprises: 1) mixing a complexing agent with metal salts in the presence of a solvent to obtain a mixed solution; 2) performing a hydrothermal reaction on the mixed solution of step 1) to obtain precursor microspheres; 3) calcining the precursor microspheres of step 2) to obtain a dual-phase hollow high-entropy oxide catalyst; in step 1), the solvent is water; the complexing agent is glucose, citric acid and xylitol; the metal salts are ruthenium salts, nickel salts, cobalt salts, iron salts, manganese salts and chromium salts; the concentration of the complexing agent is 15-135 g / L; the molar concentration of the ruthenium salt is 15-50 mmol / L, wherein the ruthenium salt is calculated based on the element ruthenium; the molar concentrations of the nickel salt, the cobalt salt, the iron salt, the manganese salt and the chromium salt are all 5-70 mmol / L, wherein the nickel salt is calculated based on the element nickel, the cobalt salt is calculated based on the element cobalt, the iron salt is calculated based on the element iron, the manganese salt is calculated based on the element manganese and the chromium salt is calculated based on the element chromium; in step 2), the conditions of the hydrothermal reaction include a temperature of 120-220 ℃ and a time of 1-12 h; in step 3), the conditions of the calcination include a temperature of 300-900 ℃, a time of 1-5 h and a heating rate of 1-7 ℃ / min.

5. The preparation method according to claim 4, characterized in that, the ruthenium salt is ruthenium trichloride and / or ruthenium nitrate; and / or, the nickel salt is selected from one or two or more of nickel chloride, nickel nitrate, nickel sulfate and nickel acetate; and / or, the cobalt salt is selected from one or two or more of cobalt chloride, cobalt nitrate and cobalt sulfate; and / or, the iron salt is selected from one or two or more of iron chloride, iron nitrate and iron sulfate; and / or, the manganese salt is selected from one or two or more of manganese chloride, manganese nitrate, manganese sulfate and manganese acetate; and / or, the chromium salt is selected from one or two or more of chromium chloride, chromium nitrate and chromium sulfate.

6. The production method according to claim 4 or 5, characterized by, in step 2), the particle size of the precursor microspheres is 1-4 μm.

7. A bi-phase hollow high-entropy oxide catalyst prepared according to the method of any one of claims 4-6, wherein the catalyst has a specific surface area of 20- 100 m2 / g, a pore volume of 0.1-0.5 cm3 / g, and a pore size of 2- 20 nm. The dual-phase hollow high-entropy oxide catalyst has an oxygen evolution potential of 180 mV~290 mV and a hydrogen evolution potential of 80 mV~180 mV under electrocatalysis at 10 mA / cm 2 ​ 8. Application of the dual-phase hollow high-entropy oxide catalyst of any one of claims 1-3 or the dual-phase hollow high-entropy oxide catalyst of claim 7 in the field of electrolytic water.

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